Re: Can a tire deteriorate internally due to age alone?
We just replaced the OEM radial tires on our 1994 Sundowner this spring. They had just started to show signs of cracking on the outer wall. To the surprise of our tire guy, there was no visible signs of internal damage when removed. But yes, there can be internal damage from aging.
Test results from the NHTSA TIRE AGING TEST DEVELOPMENT PROJECT.
There is some very interesting data in this report.
http://www-nrd.nhtsa.dot.gov/pdf/esv/esv20/07-0496-W.pdf
CONCLUSIONS
The goals of Phase 1 were to provide a better understanding of the effects of service life on tires and to serve as the ?real-world? baseline for evaluating the effectiveness of accelerated laboratory tire-aging methods in subsequent phases of the project. For the tests detailed in this paper, the following trends were observed in the Phoenix-retrieved tires:
While mean tire inflation levels of on-road tires did not deviate much with age, approximately 11% of passenger vehicle tires and 14% of light truck tires had retrieval pressures below the minimum pressures in the 2003 Tire & Rim Association Tire Load Limit Tables that were in place at the time of the tire collection.
Results of bead-to-bead shearography of the tires indicated that internal separations in the tire tended to increase with increasing age and mileage, correlating better to mileage.
In the Stepped-Up Speed roadwheel test, some tire models showed a decline in time to failure with age and mileage, while others did not. Results indicated a strong correlation to the speed rating of the tire, with the higher speed rated tires losing the least capability with increasing age and mileage.
In the Stepped-Up Load roadwheel test, all tire models showed a decline in time to failure with age and mileage. Results indicated a strong correlation to the speed rating of the tire, with the higher speed rated tires losing the least capability with increasing age and mileage.
Optical microscopy results indicated that the largest crack length measured in tire cross-sections examined tended to increase with increasing age and mileage.
The tensile properties of wedge rubber compound between the two belt edges were observed to increase in modulus and decrease in ultimate elongation with increasing age and mileage.
The average peel strength in the wedge rubber region between the two belt edges was observed to decrease with increasing age and mileage, indicating reduced adhesion between the steel belts.
The changes in the physical material properties of the tire rubber compounds can be explained by chemical changes in the compounds and interfaces; however discussion of these measures was beyond the scope of this paper.
Over 30% of the passenger and light truck tires at the spare tire location had inflation pressures below the 2003 T&RA Load Table minimums. Roadwheel tests of eight zero-mileage full size spare tires indicated possible reductions in performance with age
